Some of the bare wire of my Sennheiser 380's are exposed, how dangerous is this?

The protective outer layer of the cable has peeled a half an inch near the headphones themselves somehow. With the 380's you plug the top of the cable into the headphones input, but below this solid piece and onto the soft cable itself is where the layer has peeled away. I have had the phones for 2 and a half years.

Now the sound is coming out perfectly on both sides still, but I heard this noise coming through my cans when no music is being played. It is obviously the sounds of the wires being exposed. The cable has been like this for over a month but this inteference noise has only started today.

Should I plug out my cans from my amplifier (Matrix) when going to bed at night? And how dangerous is this?

If the wires still have the colored, rubberized shields around them, no big deal. However, if the bare wire is exposed, get some electrical tape for a temporary fix, and then have them repaired by the manufacturer.